animal experiment male nonhuman 97 priority journal unclassified drug controlled study 91 Male 77 Animals 75 article 69 animal tissue 55 animal cell 54 mouse 49 animal model 44 animal 37 Mice 35 protein expression 35 Article 32 female 32 metabolism 30 messenger RNA 24 rat 24 Rats 22 in vivo study 22 gene expression 21 Female 20 human 20 enzyme activity 19 adult 18 in vitro study 18 protein function 17